The present invention relates to a process of producing iron from fine-grained iron ores.
It is known to produce iron from oxidic iron ores in a process in which the ore is initially converted by direct reduction with a suitable gas to substantially metallized sponge iron which, with the addition of additives and possibly scrap, is melted in a suitable vessel filled with a metal melt. In the melting vessel, the reaction of oxygen-containing gases with carbon-containing substances, particularly coal and/or coke dust--which are preferably blown into the metal melt below the bath surface--produces heat and a carbon monoxide-containing exhaust gas. Some of this heat is used to melt the sponge iron and the exhaust gas is used for the direct reduction.
In order to better utilize the quantities of substances and energy to be introduced into the process, it has also been proposed to react the exhaust gas from the melting vessel in a reactor with carbon-containing substances, preferably with coal dust and with water vapor and/or carbon dioxide and, after conditioning, in particular hot dust removal, mixing it with the reduction gas, some of which is circulated in the reduction stage in a circuit including a gas processing system, and using it for the direct reduction of the iron oxide-containing raw materials, as described in U.S. Pat. No. 4,007,034.
Also known is a process which is characterized by the combination of various measures and in which the fine-grained iron ores are preheated in a countercurrent heat exchanger at 500.degree. to 850.degree. C. The fine-grained iron ores are reduced to sponge iron with the exhaust gases of the melting process, almost exclusively carbon monoxide, in a fluidized bed reactor at 500.degree. to 850.degree. C. This sponge iron has a degree of metallization from 40% to 95%. The sponge iron is then separated from the reduction gas, with the remainder of the reduction and the melting taking place in an iron melt in which oxygen, sponge iron and carbon carrier are introduced into the iron melt through multi-jacket nozzles disposed below the bath surface. The remaining reduction and the melting of the sponge iron take place in the melting vessel from which part of the molten iron is removed continuously. This is described in U.S. Pat. No. 4,045,214.